Use of a device for cleaning metal fibers with a view to recycle and recover the same

ABSTRACT

The field of the invention is the recovery and recycling of materials, particularly the recycling of tyres. It relates particularly to a device for cleaning metal fibres comprising at least 2 coaxial cones, one fixed and one mobile in rotation, and means of moving said mobile cone.

The field of the invention is the recovery and recycling of materials, particularly the recycling of tyres.

The recycling of tyres is a well known problem which is the subject of many developments.

It is known that out of approximately 400,000 tonnes (i.e. 30 million worn tyres) produced annually, 60,000 are retreaded and 80,000 start a new life in a different guise. 30,000 tonnes are burned, a significant number are used to keep covers in place on silos and only 45,000 tonnes are recycled. Thus almost 185,000 tonnes end up on rubbish tips, where the fire risk is considerable.

A tyre contains more than 200 constituents split between 5 families:

-   -   natural rubber, a principal constituent of the treads of heavy         goods vehicle tyres;     -   synthetic rubber, an essential element of the treads of car         tyres;     -   carbon black and silica, used as a reinforcing filler in order         to improve wear resistance in particular;     -   textile and metal cables constituting the belt and the bead         wires of the carcass;     -   various chemical agents         The rubber represents approximately 75% of a tyre, the textile         approximately 15% and the metal fibres approximately 10%. This         gives an idea of the weight of metal that could be recovered         annually from tyres alone.

Tyres are assembled without adhesive using methods such as calendering which incorporates the cables into the thin layers of rubber by compression between two large-diameter rollers.

The tyres can be burned, for example in cement plants.

Continuing developments are being made in recycling the rubbers in the form of aggregates. In this regard there can be mentioned as examples of use

-   -   wheels and castors (tyres and solid wheels (trolleys,         rollerblades, etc.))     -   safety surfacing and edging for play areas.     -   sports surfaces (tennis courts, athletics tracks, golf courses         (mixed with earth, etc.), equestrian surfacing (maneges, tracks,         etc.)).     -   sound insulation (anti-noise barriers)     -   base course     -   wearing course     -   roofing materials (weatherstripping, etc.)     -   interior surface coverings (tiles, reinforced carpets, etc.)     -   road signage and accessories (speed bumps, kerbs, etc.)     -   porous drainage pipes     -   rugs for animals (horses, cows, dogs, etc.)     -   and various other uses         -   in vehicles (brake linings, steering wheels, windscreen             wipers, etc.)         -   trains and tramways         -   footwear         -   manufacture of new tyres         -   water sports (flippers, snorkels, etc.)         -   leisure devices (cameras, covers, etc.)         -   highway filter drains         -   office supplies and equipment (chair backs, etc.).

Currently, worn tyres are recovered by two methods

-   -   comminution using rotary shears in order to reduce the tyres to         small pieces (chips) sized approximately 10 cm×10 cm, so that         they can be used in a furnace at a cement plant;     -   passing these small pieces (chips) through extrusion presses         which makes it possible to obtain a mixture of three fractions         -   rubber powder         -   textile fibres         -   and steel flakes.             These three fractions are then separated.

The invention relates to the third fraction, generally constituted by an extremely strong, high-quality steel.

As previously stated, the metal or textile cables are incorporated into the tyre by calendering in the thin layers of rubber by compression between two large-diameter rollers. This very high-pressure compression results in very strong cohesion between the cables and the rubber elements.

During the process of recovery of the tyres, passing the “chips” through the extrusion presses results, after separation, in the obtaining of steel flakes that are still rich in textile fibres and rubber tightly bonded to the steel itself.

As they are, these flakes of scrap are unsuitable for smelting at a steelworks. Before it is possible to recycle the steel at a steelworks, it is therefore necessary to clean it, in order to obtain a mass of steel that is approximately 90 to 100% pure (i.e. without textile fibres or rubber).

Methods have been proposed based on extremely fine shearing of the steel fibres, but these have proved relatively disappointing as contaminant materials (textile fibre and rubber) nonetheless remain adhered to the steel fibre, continuing to make it unsuitable for smelting. It is therefore understood that there is a need for a device for cleaning steel fibres originating from tyre recovery that is simple and inexpensive and results in the production of recovered steel fibres that are suitable for smelting at a steelworks.

This is one of the purposes of the present invention.

The invention is based on rubbing the contaminated steel fibres on a solid wall in order to remove from the steel fibres, by friction, all or at least the great majority of the contaminant products adhering to said steel fibres, such as for example textile fibres and/or rubber in the case of steel originating from tyre recycling.

Thus a subject of the invention is the use of a device comprising

-   -   at least two coaxial cones, said first cone or stator being         fixed and the second cone or rotor, having smaller dimensions         than those of the stator, positioned inside the stator, being         mobile in rotation about the central axis common to the two         cones, the inner wall of the stator and outer wall of the rotor         never coming into contact and arranging between them a free         space itself having a conical cross section, the lower bases and         the upper surfaces of the stator and of the rotor being         respectively situated on the same side;     -   a means of moving the rotor,         for cleaning metal fibres, particularly steel fibres, very         particularly steel fibres originating from tyre recycling.

U.S. Pat. No. 5,624,078 describes a device with which tyres can be cut into small pieces using blades fixed onto the rotor. The steel is then removed in a magnetic separator.

This device does not make it possible to clean the metal fibres so that they are acceptable at a steelworks. In fact, at the output of this device contaminated steel fibres are obtained which are merely the raw material for use in the device according to the invention.

It is therefore understood that the two cones are nested together, along their common central axis, their large bases and their small bases being located respectively on the same side, so that between them they form a space the upper opening of which (intended to receive the raw material to be cleaned) is larger than the lower opening (intended to allow the refined material to escape).

According to the invention the stator can have a height comprised between 800 mm and 3,200 mm, preferably between 900 mm and 3,000 mm.

Similarly according to the invention, the stator can have a lower circular base the diameter of which is comprised between 650 mm and 2,800 mm, preferably between 750 mm and 2,600 mm.

According to a particular embodiment of the invention, the wall of the stator can form an angle comprised between 15° and 45° to the vertical, preferably comprised between 20° and 40°.

According to a further particular embodiment of the invention, it is possible for the wall of the stator not to be rectilinear and to have a lower part and an upper part between them forming an angle comprised between 170° and 179°, preferably between 174° and 176°.

According to this particular embodiment of the invention, the lower part of the stator wall can represent between 15% and 35% of the total height of the stator, preferably between 20% and 30%.

According to yet a further particular embodiment of the invention, the wall of the rotor can form an angle comprised between 5° and 25°, preferably between 10° and 120° to the vertical.

Finally, according to a further particular embodiment of the device used according to the invention, the ratio between the diameter of the lower base (small base) of the rotor and the diameter of the lower base (small base) of the stator can be comprised between 0.82 and 0.99, preferably between 0.90 and 0.95.

Thus according to the invention, the lower base of the rotor can have a diameter comprised between 530 mm and 2,750 mm, preferably between 615 mm and 2580 mm.

According to the invention, any means of moving the rotor can be used. Mention can be made for example of a motor, optionally provided with a reduction gear, said motor possibly being an electric motor or a heat engine. The rotor can also be driven by pneumatic means. Preferably according to the invention, the means of moving the rotor is an electric motor.

According to the invention, the rotor can be moved at a speed comprised between 45 and 100 rpm, preferably between 60 and 85 rpm.

According to the invention, the stator/rotor assembly can be placed on a base providing that the latter has an arrangement for the refined material to pass through.

Preferably according to the invention, the assembly is cantilevered. It is understood that in this arrangement the assembly is held laterally by any fastening means. In this arrangement, the drive means of the rotor is preferably situated in the upper part of the device assembly.

According to the invention, the rotor can be a solid cone or hollow internally. For practical reasons, the rotor is a cone that is hollow internally.

Of course, a person skilled in the art will know how to use suitable materials to produce the walls of the stator and/or of the rotor. He will preferably use the materials generally used in the field of machine tools, if only so that the device according to the invention can withstand the stresses imposed by its function (resistance to friction, pressure, corrosion, oxidation, etc.) such as for example steel, particularly stainless steel, or also carbon steel. Thus according to the invention, the walls of the stator and/or of the rotor can be, simultaneously and/or independently, made of steel, particularly stainless steel, or also carbon steel. Preferably according to the invention, the walls of the stator and/or of the rotor can be made of steel.

According to a variant of the invention, the stator wall can be made of concrete. In this particular configuration, the walls of the stator and of the rotor will not be made of the same material and the wall of the rotor can be made of steel, particularly stainless steel, or also carbon steel.

With respect to the gauge of the materials used, there again a person skilled in the art will have no difficulty in determining the thickness of the walls constituting the stator and the rotor according to their respective dimensions and the stresses that they must undergo.

According to the invention, the walls constituting the stator and the rotor can, for example simultaneously and/or independently, have a thickness comprised between 10 mm and 200 mm, preferably between 15 mm and 100 mm.

Finally, each of the walls, simultaneously or independently, can be constituted of a single piece or several pieces. A person skilled in the art understands that it is preferable for the walls, which are subject to wear as a result of friction and which must therefore be regularly replaced, to be in several pieces that are easily disassembled when it is necessary to replace them. The number of pieces constituting said walls is not an essential element of the invention. A person skilled in the art will know how to adapt the number of pieces according to the stresses encountered.

The inner wall of the stator and the outer wall of the rotor can be, simultaneously or independently, smooth or ribbed. Preferably they are ribbed, which provides better friction. If they are ribbed, the ribs are advantageously oriented vertically in order to facilitate the downward flow of the material.

A further subject of the invention is a method of cleaning metal fibres, particularly steel fibres, very particularly steel fibres originating from tyre recycling, using a device as described previously, in which the raw material to be cleaned is introduced into the space arranged between the stator and the rotor of the device according to the invention, through the upper opening, the rotor being driven in rotation at a speed of 70 rpm, and at least the refined material is collected on leaving the lower opening of the space arranged between the stator and the rotor, on the lower part of the device, said material possibly being mixed with the residue of contaminants removed from the surface of the raw material to be cleaned.

Finally, a subject of the invention is the use of a device according to the invention, comprising a stator and a rotor in the form of cones, said cones being nested together along a common central vertical axis, and a drive means of the rotor,

-   -   said stator having a height of 950 mm, having a lower base of         800 mm, the wall of said stator being made of steel 15 mm thick,         non-rectilinear, having a lower part reaching a height of 200 mm         with a angle of 20° to the vertical and an upper part, meeting         the lower part, reaching a height of 750 mm with an angle of 25°         to the vertical, the lower part and the upper part between them         forming an angle of 175°,     -   said rotor having a height of 1,000 mm, having a lower base of         750 mm, the wall of said stator being made of steel 15 mm thick,         rectilinear, forming an angle of 25° to the vertical.

The invention will be better understood with reference to the attached FIG. 1 which diagrammatically represents a device according to the invention.

FIG. 1 shows a device according to the invention in which the stator (10), the rotor (11) and the drive means of the rotor (12) are represented.

The upper opening (13) and the lower opening (14) of the space (15) arranged between the stator and the rotor can be seen.

It is also apparent that in the device shown, the wall of the stator is not rectilinear, having an angle (α) of 155° on the lower part. 

1. A method of using a device for cleaning metal fibres, the device comprising at least two coaxial cones, said first cone comprising a stator being fixed and the second cone comprising a rotor, having smaller dimensions than those of the stator, positioned inside the stator, being mobile in rotation about the central axis common to the two cones, the inner wall of the stator and outer wall of the rotor never coming into contact and arranging between them a free space itself having a conical cross section, the small bases and the large bases of the stator and of the rotor being respectively situated on the same side; a means of moving the rotor, for cleaning metal fibres, particularly steel fibres, very particularly steel fibres originating from tyre recycling.
 2. The method according to claim 1, wherein the wall of the stator is rectilinear.
 3. The method according to claim 2, wherein the wall of the stator has an angle comprised between 15° and 45° to the vertical, preferably comprised between 20° and 40°.
 4. The method according to claim 1 wherein when the wall of the stator is not rectilinear, the wall has a lower part and an upper part between them forming an angle comprised between 170° and 179°, preferably between 174° and 176°.
 5. The method according to claim 2, wherein the lower part of the stator wall represents between 15% and 35% of the total height of the stator, preferably between 20% and 30%.
 6. The method according to claim 1, wherein the wall of the rotor has an angle comprised between 5° to 25°, preferably between 10° to 20° to the vertical.
 7. The method according to claim 1, wherein the ratio between the diameter of the small base of the rotor and the diameter of the small base of the stator is comprised between 0.82 and 0.99, preferably between 0.90 and 0.95.
 8. The method according to claim 1, wherein the means of moving the rotor is an electric motor or a heat engine or also a pneumatic means.
 9. The method according to claim 1, wherein the rotor is moved at a speed comprised between 45 and 100 rpm, preferably between 60 and 85 rpm.
 10. The method according to claim 1, wherein the walls of the stator and/or of the rotor are simultaneously and/or independently made of steel, particularly stainless steel, or also carbon steel.
 11. The method according to claim 1, wherein the walls of the stator and/or of the rotor, simultaneously and/or independently, have a thickness comprised between 10 mm and 200 mm, preferably between mm and 100 mm.
 12. The method according to claim 1, wherein the walls of the stator and/or of the rotor, simultaneously or independently, are smooth or ribbed, preferably ribbed, very preferably vertically ribbed.
 13. The method of cleaning metal fibres, using the device according to claim 1, in which the raw material to be cleaned is introduced into the space arranged between the stator and the rotor of the device according to the invention, through the upper opening, the rotor being driven in rotation at a speed comprised between 45 and 100 rpm, preferably between 60 and 85 rpm, and at least the refined material is collected on leaving the lower opening of the space arranged between the stator and the rotor, on the lower part of the device, said material possibly being mixed with the residue of contaminants removed from the surface of the raw material to be cleaned.
 14. The method according to claim 1 of the device, wherein said cones are nested together along a common central vertical axis, and the means of moving the rotor comprises a drive means for the rotor, said stator having a height of 950 mm, having a lower base of 800 mm, the wall of said stator being made of steel 15 mm thick, non-rectilinear, having a lower part reaching a height of 200 mm with an angle of 20° to the vertical and an upper part, meeting the lower part, reaching a height of 750 mm with an angle of 25° to the vertical, the lower part and the upper part between them forming an angle of 175°, said rotor having a height of 1,000 mm, having a lower base of 750 mm, the wall of said rotor being made of steel 15 mm thick, rectilinear, forming an angle of 25° to the vertical. 